The sky is pitch-black at a school-bus stop in Olney, and it might as well be midnight for 15-year-old Joe Palmer. His eyes are open, but his brain feels stalled. He wishes he were still in bed. It is 6:30 a.m., with sunrise still an hour away.

“I’m pretty much a zombie,” he says as his bus pulls up. He drags himself aboard, bound for Sherwood High School.

The teen’s lament is familiar across Montgomery County, where the opening bell of high school rings at 7:25. But such pre-dawn travails have taken on more urgency in recent weeks, propelling a burgeoning effort to change the hours of the high school day.

Supporters say a growing body of sleep research shows that teens are biologically wired for later bedtimes and later wake-ups. And studies show that lack of sleep is linked to lower academic performance, absenteeism, and an increased risk of depression and car crashes.

Another danger was at issue this week, too: A student was fatally struck by a car at 7:03 a.m. as she crossed busy Route 118 in the dark on her way to Seneca Valley High School. Some parents wonder if the early school-opening hour was a contributing factor.

“It’s dark out — and it’s not safe,” said parent Shelly McGill of Bethesda.

Beth Newman, who has 14-year-old twins at Magruder High School in Rockville, said her husband, who is in charge of morning wake-ups, uses an array of tactics to rouse their slumbering sons: flipping on the lights, turning up the radio, threatening to keep them from activities. “It’s just torture. It’s a constant struggle,” said Newman, who works as a substitute teacher in Montgomery and has seen teens fall asleep in class, especially during first period.

Other students nap after school. They ask parents for rides, rather than take the bus, so they can sleep in as long as possible. One Kensington teen says being tired is one of the most discussed topics of every school day.

Mike Kramer, 16, a junior at Walter Johnson High School in Bethesda, started a Facebook page on the issue last year on a night when he had “seven to eight hours of homework and I was up to 2 a.m. and I had to get up at 6.”

Fairfax — with start times at 7:20 a.m. — debated the issue in the late 1990s and again several years ago. Montgomery has looked into it at length, too. Arlington County, a much smaller school system, launched new school-bell times in 2001: Three of its high schools now start at 8:19 a.m. and a fourth at 9:24 a.m. Loudoun County schools start at 9 a.m.

In Montgomery, the recent effort was started by Mandi Mader, a mother of two and a psychotherapist who found that a lack of sleep exacerbated the problems of her adolescent patients. Her own children were dragging in the morning, too, she said, even though she enforced strict bedtimes.

“MCPS does so much right,” Mader said, “but I think they’re behind the curve and not up to best practices on this.”

Mader raised the issue on an e-mail discussion group run by parents at Walter Johnson. And she hit a nerve.

Soon, she and others formed a Montgomery chapter of the national group Start School Later. The group is pressing the issue as a public-health concern — comparable to seat-belt use or secondhand smoke — and is seeking change through federal legislation or regulations. More than 7,000 people from Clarksburg to Silver Spring have signed the Montgomery petition.

Nine days after it went up, Superintendent Joshua P. Starr commented on it while on “The Kojo Nnamdi Show” on WAMU (88.5 FM).

“I get it. I understand the thinking behind it,” Starr said. He pledged to “dust off” a 1998 study of start times but added that he has heard mixed reviews from school systems that made a change.

In Montgomery, “we have goals for the year,” Starr said. “We’re focusing on teaching and learning. This is a huge undertaking. Will it take us off-task? The school board has to consider that.”

Previous efforts in Montgomery included intensive study and a range of options, said Patricia O’Neill (District 3), a school board member whose tenure goes back to 1998. The best option, she said, was to buy more buses and hire more drivers, but the cost was prohibitive. “Do you buy more buses or hire more teachers?” she asked.

“There are no simple answers,” O’Neill said, noting that concerns were raised about teens’ after-school jobs and families that depended on teens to care for younger siblings while their parents worked. Some advocates of later start times suggested that younger children be the first ones taken to school, but many objections were raised about them walking or waiting for buses in the dark.

Susan Berkheimer, the PTSA president at Sherwood, said early start times may not be ideal but that when she was a teen, school started early. High school students need to grow up, she said. “How are they ever going to have a job?”

She also said a later start could conflict with high school sports. “Everybody thinks they want their kids to sleep, but is it really worth it for an hour?” she asked.

Experts say an hour of sleep a night does make a difference.

Mary A. Carskadon, a Brown University medical professor and director of the E.P. Bradley Hospital Sleep Research Laboratory, said biological changes that come with adolescence push teens’ sleep cycles later into the night. Using computers and cellphones late at night can make falling asleep more difficult, she said.

But most teens would need to call it a day at 9 p.m., she said, to get a solid night’s sleep of between 81/2 and 91/2 hours in a school system like Montgomery’s or Fairfax’s. “What 15-year-old do you know who would go to bed at 9?” Carskadon said.

Early start times can have financial costs, too. “How much money are we wasting in instruction time when kids are sitting there foggy-brained or literally asleep?” asked Fairfax County School Board member Sandy Evans (Mason District).

Many families eye Loudoun’s 9 a.m. start time wishfully.

“I think the kids there get more out of their classes,” says parent Debra Felix, who has visited both Loudoun and Montgomery schools and sees a difference in “how alert and happy and awake” teens are when they arrive in the morning.

For Joe Palmer, school-day wake-up starts at 5:30 a.m. in his Olney home.

Often, his mother wakes him and makes him sit up, only to return and find him sleeping with no memory that she ever came into his room. He rushes out with breakfast in hand — a sandwich — and often is so delayed that he asks for a ride.

His twin sister, Fiona, carries a favorite pillow onto her bus so she can grab 40 minutes of slumber en route to Gaithersburg High School.

For Joe, the bottom line is simple: “I need more sleep.”

Donna St. George writes about education, with an emphasis on Montgomery County schools.

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